The Atomic Bomb
by Quaggy
Summary: "Derek could only see one course of action. He and Casey needed to meet their family's delusions and raise it with denial that those delusions even existed." Post-series Casey/Derek.


Title: The Atomic Bomb  
Originally Published: September 21, 2016  
Notes: Ed's a little meaner here than I normally write him.

* * *

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During Christmas of their senior year of high school, Liz and Ed had a big falling out. But afterwards it was Casey who was still reeling.

"I don't know why I can't let this go," Casey told Derek as they drove back to Queens. "Lizzie's fine and so over it, but I still feel awful for her."

"Yeah, I know. You've been talking about nothing else for two hours," Derek grumbled.

"Sorry."

"I just would like to talk about something different, Case. We've got a long drive ahead of us and I would rather not spend the most of it thinking about how I wanted to smack my own brother with a 2x4."

"You were upset too!" Casey realized with astonishment. Not because she was shocked that Derek cared. (She had long learned to look past his posturing to see the guy with the big heart hiding behind.) But rather, because Liz was her sole focus, she lost track of how everyone else was reacting.

"Of course, I was upset! Do I understand where Ed was coming from? Yeah! It sucks not to have someone you like reject you, especially after being given all indications to the contrary. And the fact that she used Ed being close to Lizzie as her excuse was a low blow. But Ed did not have to then keep harping to everyone on the planet how he could never imagine dating Liz and all the reasons why."

"Yeah, up until that point, I was really feeling sorry for him. Then I was just feeling sorry for Lizzie."

"You don't think that she. . . ." Derek's voice trailed off.

"No! At least, I don't think so."

"I think Ed might."

"You're kidding!"

"How does it go? ' _Me thinks the lady doth protest too much'_."

"Well, I'm impressed. And here I thought you slept through that unit."

"Don't tell anybody."

"Like anybody would believe me. It's just strange that Lizzie and Edwin are having to deal with this at all. No one ever asked either of us if we were dating back in high school."

"Probably too afraid," Derek said, with a rueful half-smirk.

"Afraid that we'd start listing the reasons why we hated each other?"

"Afraid we'd realize that there was only one good reason why we shouldn't be together."

"Like we both didn't know that already," Casey scoffed. Derek's eyebrows rose. "Or am I wrong?"

"No," Derek replied quickly. "It was just weird to hear you say that out loud."

"You started it."

"Ed started it."

"Okay, fair point," Casey conceded. Both fell silent after that, thinking about things they probably shouldn't.

"It's a very good reason," she finally said, quietly.

"True."

"Forever seems a lot more scary than romantic when you think about how long the human lifespan is."

"Also true. Even ten years is a very long time to commit when you don't know if you'll still like the same bands in two weeks."

"Exactly," Casey sighed. "As much as I would like to say that we could both be mature and cool if we broke up. . . ."

"Our collective track record says otherwise," Derek nodded, somewhat rather ruefully."If course, we _could_ just last long enough for everyone else in the family to die first— OWW! Casey, don't hit the driver!"

"That's so not an option."

"I'm just saying. . . ."

"You ever heard that creative people live longer?"

"Which means Marti will never die," Derek grinned, instantly catching Casey's drift. "Okay, so out-living everyone is a no-go. Which means, we'd just be dooming the family to a lifetime of awkward, family get-togethers and. . . ." Derek trailed off, self-consciously.

"And?"

"And I don't think I could stand not having you in my life," he admitted roughly. He glanced over when she didn't say anything. "Come on, Case. Don't look so shocked! I followed you to Queens. And you can bet I'm going to follow you to Toronto, even if I'm not crazy enough to follow you all the way to law school too. I think it's pretty clear that I want you in my life."

"That frighteningly sounds like a declaration of affection."

"Or enough for you to take out a restraining order."

"I want you in my life too, Derek. And I'm really terrified that getting together might be the only thing that could drive us apart for good."

"So we just go on like we always have, because it's better than nothing?"

"I don't see how we really have any other choice."

They exchanged rueful grins. After traveling in silence for a bit, Casey brought up a TV show that they both watched and Derek happily participated in the distraction. Soon they were bickering as usual and the trip back to campus went quickly. But Derek grew solemn as they pulled into the nearest parking lot to the dorms.

"Derek, what's wrong?" Casey asked, noting his strange mood. Derek didn't respond he parked the car and turned it off.

"Case, this doesn't leave the car, okay?" he asked, nervously. When Casey nodded, Derek leaned over and kissed her softly. The kiss was not at all brief, but it was gentle. An expression of devotion more than one of passion. When he finally pulled back, Casey opened her eyes as soon as she was certain she wouldn't cry. Her smile was adoring.

"I just wanted to. Just once," he shrugged.

"Me too. I'm glad we did," Casey agreed, touching her forehead to his for one long moment. Then, with a sigh, she opened the car door.

They were both gratified when they were able to act completely normal after that. They still met for lunch, went out with friends, and did all the things that they had gotten in the habit of doing together while they were in college. There was no tension or longing looks. Quite the opposite. The happiness in what they did have totally overshadowed the ghosts of what could have been. They really were able to leave that kiss behind them in the car. Until he came over for dinner one night, a few months later. She leaned over to kiss him hello . . . and something snapped. They were kissing. Really kissing. And then. . . . Well, they made it to the bed eventually.

Much later in the evening, after they had ordered a pizza, they finally got around to talking about where they were going to go from here. It was very clear that whole staying away from each other romantically wasn't going to work anymore. And putting their family through the drama of a big break-up wasn't an option any more than it had been when they first discussed things. That really did leave only one possibility.

They were children of divorce. And while their parents did seem to be doing much better with all things matrimonial this time around, neither Derek or Casey were foolish enough to think that the first Venturi-McDonald marriage was a foolproof model to emulate if they were thinking of producing a sequel. And that meant was that they were two kids staring down "'til death do us part" without any idea of what that actually looked like.

"Maybe we should talk to Paul," Casey mused.

"Paul who?"

"Paul Greebie. You remember? Our guidance counsellor during high school?"

"You mean, he didn't take out a restraining order after you graduated?"

"Do you want to be a smartass or do you want to talk about this seriously?"

"I can do both."

"Paul might be able to suggest a good pre-marital counsellor. Someone who can help us figure out how to stay together," Casey explained. "Or help us figure how to contain the damage when this blows up in our face," she added as she slapped Derek's hand away from her remaining slice of pizza. (She had claimed three slices and had let him have the rest. You think he would have been happy with that.)

"I suppose you've had worse ideas," Derek reluctantly agreed. "At least, with all he saw, he's probably not going to be all that shocked."

Paul wasn't even a little bit shocked. He had seen this one coming ages ago and sounded really pleased for them. And he had a surprising offer.

"I'm certified to practice in family therapy and I know you both. It might be easier for you in the beginning to talk with someone who has already witnessed a bit of your history first-hand. You'll be back in London for the spring break, right? We can start then."

The most surprising thing that came from the therapy sessions was how prepared Casey and Derek were for the compromise and cooperation of a long-term relationship. But, as Paul pointed out, they had been learning how to do that since they were fifteen. It wasn't totally smooth sailing, but they had a good foundation. Both were willing to do what it took to have a strong relationship and were grateful that Paul was able to show them how.

The sessions lasted through the summer until Casey moved to Toronto to get settled before law school started, with Derek staying behind in London to finish his internship. They were a little worried they would have to be long-distance for a while. With Derek seriously pursuing sports journalism, he was going to need to go wherever he managed to get a job, even if it was across the country. But Derek's amazing luck held out. He was able to get an entry level position at one of the news stations in Toronto. It was mostly low-level behind-the-scenes stuff, but Casey had no doubt they'd have him on camera before long. Derek had great screen presence and, more importantly, he knew his stuff. Even though they were both going to be in Toronto, they talked about getting separate places for a while, but it didn't make much sense. They were ready for the level of commitment that came with living together and the separate places would be more for show than from a need for the time and space.

They both decided (and Paul agreed) that if they were ready to move in together, then it was finally time to announce that they were a couple to their friends and family. But that meant they had to deal with the problem that comes when you start getting serious about someone that you've known for years, specifically how to tell everyone without it being awkward or embarrassing. There's always the risk that you cross the "Too Much Information Barrier" and cause eternal trauma for all concerned.

The best option was to hope that everyone has already noticed your (not so) carefully hidden feelings and had been waiting for you to get together. And while things played out like that with most of their friends, they knew that the likelihood that their family would be as aware of things was as a long-shot. From the moment that George and Nora got married, they assumed that their legal document would magically erase the teenage hormones of their children. It wasn't just that they trusted their kids. It's that the idea that Casey or Derek could ever even look at each other in a romantic light never seemed to cross their minds. There was absolutely no doubt in both Casey and Derek's minds that if their parents had even considered it then they would have made some very different decisions along the way. (They left the two of them alone in the house during spring break, for crying out loud!)

The next-best option would be to blurt it out right after something significant, but not too graphic happens. But the only thing that really qualified for that was that first kiss in the car. Which came after a long conversation about why they never could be together. Why raise a fuss over a good-bye kiss? And things had gone from zero to fully-committed after that.

So they were going to have to go with their least favourite option: the bombshell. They chose one night at dinner when the entire family was sure to be home and just went for it.

"I have announcement to make," Derek said, standing up at the table with his usual cocksure attitude. "Casey and I are moving in together."

"Casey, you're moving?" Nora asked, turning to her daughter in surprise. "I thought you loved your apartment."

"No, no. I do love my apartment. I'm not going anywhere," Casey quickly replied. "We're just moving in together. I mean, technically, Derek's moving in with me, but we're moving in together."

"Oh, okay. That makes more sense," Nora replied. Casey and Derek waited, but that seemed to be the extent to everyone's reactions.

"Okay. . . . That's it?" Derek asked, with a hint of trepidation, "That's all you people have to say?"

"Well, to be honest, son, I think we've all been expecting something like this to happen," George shrugged.

"Yeah," Lizzie chimed in. "It was pretty easy to figure out. You were always over at Casey's when you were back at Queens and you looked so lost when she moved to Toronto without you."

"Well, alright then," Derek said, completely nonplussed, and looked over at Casey who shrugged. "Guess I'll just sit down then." Exchanging grins, the two went back to their meal. That was easier than either one was expecting.

Except it wasn't.

Because as obvious as Casey and Derek thought they had been, they had underestimated just how oblivious their family could be. In a classic case of two and two equals five, their family thought that Derek and Casey were moving in together in Casey's one-bedroom apartment, _as siblings_. Of course, neither realized this until a few months later, when George, while watching a hockey game said something about how maybe Derek should start looking for his own place.

"After all, you can't sleep on your sister's couch for the rest of your life," George added, rising to get another beer from the kitchen.

Derek had been too dumbfounded at the time to respond. And what was he supposed to be saying anyway? "Actually, Dad, I sleep in my sister's bed" or something like that?! He might as well call 9-1-1 while he was at it, seeing as George would have a heart attack as soon as the words registered. There was no good way to start this conversation, even though something definitely needed to be done. Derek decided it would be so much easier if he let Casey do it.

Not that Casey fared much better. She had picked a quiet time when she and Nora were alone in the kitchen. The plan was to ask her mother for relationship advice and, with any luck, subtlety enlighten her about her daughter and step-son's true relationship in the process.

"I figured it would be a good time to have overdue mother-daughter chat," Casey began, channelling her younger obsessive-compulsive self. "Especially now that I'm starting a household of my own."

"Oh honey, I don't think you have to stress yourself out so much. It's just Derek. I don't think you have to do anything special."

"Yes, but this is different. This is significant."

"Honey, Derek's family. Don't worry so much."

"Mom, you know that Derek and I are together, right? Like _together_ together," Casey finally asked in exasperation and then grimaced at the inelegant phrasing. She was an English major for crying out loud! Wasn't she supposed to be more articulate than this?

"Of course, dear," Nora said absently, quickly followed by a panicky "SIMON!" and she ran off to stop her youngest from swinging on the chandelier in the dining room before Casey could say another word.

Casey tried a few more times after that, but those were even bigger failures, if possible. Since the direct approach didn't work (and probably wouldn't work if Simon was anywhere in the near vicinity), Derek could only see one course of action. He and Casey needed to meet their family's delusions and raise it with denial that those delusions even existed. In other words, he and Casey would act like everyone already knew they were a couple and, sooner or later, everyone else would wise up. Casey wasn't sure what she thought about his plan. She was half convinced that she and Derek could have a big, white, cathedral wedding and proceed to have a dozen kids and their family would _still_ find a way to classify their actions as typical sibling behaviour. But it certainly made things easier for the two of them, so denial it was.

And denial it would be for nearly a year and probably would have been for years to come if not for the fact that Ed, after a fairly rough freshman year, had managed to land himself a girlfriend during his first few months back at university. A serious, "grown-up" girlfriend, who had agreed to come to stay over Christmas vacation. He could talk of nothing else the entire the time that everyone had come home for a long weekend to celebrate Simon's 5th birthday. While George and Nora were fine with his girlfriend coming to visit, they drew the line at the two sharing a room. Edwin, who clearly hadn't gotten the "Too Much Information" memo, spent the rest of the weekend trying to change his parents' minds. (And if this what Ed was like when he was getting some, Derek, for one, was about to forcibly ship him off to a monastery.) Even during their last dinner together, Ed was still at it.

"As a mature adult, I should be treated as one," he had argued.

"Casey and I have been living together for over a year now and you don't see us trying to share a room," Derek scoffed. There had been some room shuffling right before Derek and Casey's started college. Edwin and Derek had swapped and Liz had gotten the largest bedroom since she and Casey would have to share when the entire family was home.

"My relationship with Mackenzie is nothing like yours and Casey's," Edwin in a superior tone of voice that would have gotten him killed if Derek didn't find the irony of that statement so amusing.

"Yeah, Casey and I will still be talking to each other in three months, while you—"

"Actually, I think Derek might have stumbled on the solution," Casey interrupted in her most diplomatic voice. "What if I room with Derek and Mackenzie can sleep in Liz's room the weekend that she's here?"

"I have to share with Edwin's girlfriend?" Liz asked sceptically. She and Edwin had made their peace before they graduated from high school, but they never regained their past closeness. Going to university on separate ends of the country only acerbated the problem. It wasn't that surprising. Even before their big blow up, it had been very clear that they were growing into two different people. They rarely had friends or interests in common, unlike Casey and Derek who always seemed to eventually share everything. (Casey regularly watched hockey games with Derek and Derek actually enjoyed going to see musicals and theater productions with Casey.)

"Yes. It'll only be for a few days and that way you'll have your room to yourself for most of your vacation," Casey explained. Liz instantly brightened.

"You room with Derek?" Nora said, mildly disturbed. "I'm not sure that's such a good idea."

"It'll be fine, Mom," Casey sighed. "I'm sure Derek can control himself for however long we stay."

"Me?!" Derek squawked indignantly. "You're the one that woke me up at three in the morning becau―"

"Der-rek!" Casey hissed with a deliberate look at the younger members of the family.

"Because you wanted ice cream," Derek smoothly substituted.

"Why would Casey wake you up if she wanted ice cream?" Marti asked.

"Because he sleeps on the couch in her living room, stupid" Ed snarked. (And now Ed was picking on Marti. Seriously, a monastery was too good for him.)

"ED! Don't call your sister stupid!" George yelled.

"I didn't see you complaining at the time, Derek" Casey said darkly.

"And I'm still not. I understand that women have needs and that cravings for ice cream cannot be ignored. I'm pointing out that I'm not the only one that will need to exercise some control."

"So noted. But _the point_ is that Derek and I are used to sharing a space, so a little bit of cramped quarters won't bother us."

"Right! Problem solved! Can we talk about something else now?" Derek asked in frustration.

"But Mackenzie and I want to share!" Edwin objected.

"ENOUGH!" George roared. "There will be no co-ed roommates in this house unless they are married first!" Edwin opened his mouth to argue some more, but Derek interrupted before he even got a chance to make a sound.

"That is an excellent idea, Dad" Derek pronounced and then turned to Casey with a smirk. "What do you say, Case? We've been shacking up long enough. We might as well make it official." Okay, she wasn't expecting _that_. Derek was _good_. There was really only one way to respond such a lame proposal. So that's exactly what Casey did.

"DER-REK!" she screeched and threw her roll at his head. Derek just laughed, as he caught the weaponized carbohydrate.

"I'll take that as a yes," he announced, taking a large bite out of the roll as a punctuation point (and possibly, maybe, to hide the fact that he was too happy to keep smirking.) Casey fought down a grin and kept her eyes on her plate. She didn't say anything, because she had a feeling that if she tried (or if she even glanced in Derek's general direction), she'd start giggling like a mindless idiot. Conversation resumed around the table when it was clear that she wasn't going to object to Derek's arrogance. (Why would she object? That _WAS_ a yes.)

"Should I be offering congratulations?" Marti asked, either getting an inkling about her brother and step-sister's true relationship or wanting to provoke a fight for the entertainment value.

Casey looked up at her step-sister and then glanced across the table. George and Edwin had resumed their argument. Lizzie was rolling her eyes, apparently having had more than enough of the conversation. Nora had jumped up to stop Simon from launching his peas across the dining room. Not even a marriage proposal was enough to shake their family's obliviousness and, honestly, she hadn't expect anything different. Derek was good, but he wasn't _that_ good. After all this time (and all the innuendo), Casey was convinced it was going to take something as subtle as an atomic bomb.

"I think you're better wait until he gets me a ring," Casey grinned, ruefully. But then Derek flashed his I-know-something-that-you-don't smirk and Casey realized that he was one step ahead of her.

Damn, he _was_ that good.

He got up to get something out of his coat pocket and didn't even bother to sit down before he tossed Casey the ring box. She started to make some crack about Cracker Jack boxes and gumball machine rings as she opened the box, but her voice suddenly died on her and her smile was replaced with a look of utter disbelief. Because that wasn't just any ring. It was THE ring. The one Derek wasn't suppose to know about because it was too expensive. The one that she had fallen in love with when she went with Ralph to the jewellery store to help him pick out a birthday present for his girlfriend. (It turned out that Ralph was an excellent accomplice when it came to plotting to make someone happy. And, as an added bonus, nobody would suspect him of having an ulterior motive, because he's Ralph!) The amount of planning and scheming that Derek must have gone through to make this all happen was staggering.

"DE _REK_ ," Casey breathed, pouring into those two syllables every iota of shock, awe and love welling up inside of her.

Dimly, Derek was aware that the rest of the table was frozen in silence, because Casey had never said his name like _that_ before. At least, not when any of them were around. Even Derek had only heard Casey say his name like _that_ a handful of times (and he had worked damn hard to earn each one.) He realized that they might have finally found that nuclear bomb that Casey kept saying they needed, but he quickly forgot about all of that because Casey was out of her chair and around the table and in his arms and his chair was knocked over and they were on the floor.

He tenderly pushed her hair away from her face. Her cheeks were flushed and her eyes were shinning. Even though he had intended to let his lame non-proposal stand alone in its utter perfection, he found himself going for the traditional and sappy anyway.

"Casey McDonald, will you marry me?"

"Yesyesyesyesyesyesyesyesyesyesyesyes," she chanted until his mouth covered hers.

"I thought you were saving up for a new sound system," she sighed, when they finally broke apart.

"Well, I couldn't exactly tell you I was saving up for a ring," he chuckled, taking the ring box from her and sliding the ring on her finer. His voice was low and intimate. "It would've ruin the surprise, dummy."

"Dork," she smiled, resting her forehead against his.

"Freak," he answered with a grin of his own, as he pulled her a little tighter.

Suddenly, they remembered that they were sitting on the floor in the dining room of their childhood home and that world did indeed have more people in it than just the two of them. In fact, six of those people were staring them in stunned silence. (Well, five of them were staring in stunned silence. Simon had returned to his pea hurling, which was far more interesting.)

Derek and Casey scrambled to their feet, straightening clothes and fixing their appearance. When they had more or less made themselves presentable, Derek put his arm around Casey and they turned to face their family.

"I have an announcement to make," Derek said with his cockiest grin firmly in place. "Casey and I are getting married." This time their news was met with the shocked reactions they had expected a year ago.

"Congratulations!" Marti said brightly, the first to adjust to the reality shift.

"Oh my God!" Lizzie exclaimed. "You actually _are_ together! Of course, you're together! That makes so much more sense! I thought you guys were just doing some weird act-like-we're-a-couple-to-get-a-reaction thing" Bubbling with laughter, she jumped up to hug them both. Marti crashed into all three of them moments later.

"When did this all happen?" George demanded, more shocked than upset.

"At least a year ago," Nora answered quietly, as everyone returned to their seats. "Remember? They did try to tell us. We just weren't listening."

"Casey didn't wake you up because she wanted ice cream," George said, suddenly. It wasn't a question.

"No, she didn't," Derek said, completely unembarrassed. He had been circumspect for their parents' benefit, but hey, if he had know George and Nora were that open minded, he would have stuck his tongue down Casey's throat in front of everyone a year ago and let that take care of things.

"I'm going to pretend that she woke you up because she wanted ice cream," George said after a moment's pause. Nora nodded her emphatic agreement. (So, maybe it was a good thing Derek hadn't gone with the "tongue down the throat option", after all.)

"What are you guys talking about?" Ed demanded.

"I think Derek and Casey just blew your argument to smithereens," Marti observed.

"Don't feel too bad, Ed," Liz grinned. "You were right about one thing. Your relationship with Mackenzie really _is_ nothing like Derek and Casey's."

In the end, Casey and Derek were the ones who had earned their happy ending, but it was Liz who finally had the last laugh.


End file.
